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Friday, February 13, 2015

Wherever have they been during all the hot dry days of
summer and the cold of winter?!! But here they are; back again, singing in the night. Night falls and first tentatively, then in earnest the
frog chorus begins.These are tiny
Pacific Tree frogs – but they produce the sound of a brass band!We do have other species in our locale – in
deep cold ponds we have bullfrogs, and in ponds and streams there are spotted frogs and
red legged frogs.

Pacific Tree Frog

Most of us have a
positive good feeling about frogs– whether we learned of them from Kermit on Sesame
Street or what we remember from high school biology.Maybe you were lucky enough to grow up with
frogs living nearby in a pond. I associate frogs with the warm days of spring and
summer – I think of them as fascinating but secretive little fellows.

1.Frogs and Toads
are entirely different species.Frogs
are adapted to spend their life in and close to water. Toads are adapted to
live on land…but they need moist settings.They both must lay eggs in a similar manner in water.

Pacific Toad

2.Handling frogs or
toads will not give you warts.When you
pick one up they are not coated with mucous like a fish; their skin is leathery
and wet…They feel cold because they are ectothermic– meaning that they take on
the temperature of their surroundings– heat is not generated within their
body by metaboolism.Being an endotherm like us takes a
lot of work to eat enough more to generate all the heat that we need to stay
warm.

When I taught Biology, it was traditional every year to
receive big sealed buckets of dead frogs stored in formaldehyde, The smell was
so strong that it burned the nostrils!I
stored my frogs in fresh water for a day to remove some of the smell.The organ systems of the frog are similar to
those in the human and after studying human biology; it was fascinating for
students to dissect the frog and see the same organs arranged in a complete
organism.

Frog organs

There are significant differences –mostly in scale and
size.The frog heart has only 3 chambers
– not four like ours, which results in a less efficient transfer of oxygen
throughout the body. (In addition the frog gains most of his or her oxygen directly from
the water through their skin). They have a big long stomach, 3 lobes to their
liver, 2 lungs, underneath the small intestines a small long ribbon-like
pancreas, gall balder, urinary bladder, and reproductive organs.The unlucky students who received a female
find them loaded with eggs (unlucky because it was a lot of work to remove them).

Frog eggs - after they are released in water -

The mouth of the frog had an opening to the
glottis that leads to the lungs; there are also openings to the vocal sacs,
which permit air to vibrate the vocal apparatus to produce the famous “ ribbit”
sound… Since frogs have no diaphragm to breath they have to inflate the mouth
sac (bottom of jaw) and force air into the lungs through the glottis.Its even possible to study the regions of the brain if you are a good
surgeon and can cut carefully through
the bone… (I know some of you are my ex-students – does this bring back
memories?)http://www.biologycorner.com/worksheets/frog_alternative.html

Spotted Frog

So now when I hear my little Pacific tree frog friends I can
visualize all of these systems doing just what they are supposed to do to lead
to a happy healthy frog singing through the night

Frogs are also the “Canary in the coal mine” so to speak – Large
numbers of highly abnormal frogs are being recently found – especially in
polluted water – particularly in water polluted with vast amounts of plastic
pollution.A scientist in his laboratory
was studying the effects of sex hormones on organisms… He had the apparatus set
up and returned to do the experiment.

Mutant frog

He
checked his pure solutions one more time before the test and discovered that
one was polluted with a female sex hormone – Impossible he said – this was pure
when I set it us… through tests he established that water in contact with his
plastic tubing had gained a chemical that mimics the hormone effect.Think of a swamp with plastic bags and
bottles contaminating the water. http://www.scientificamerican.com/article/plastic-not-fantastic-with-bisphenol-a/
Other chemicals also have mutagen (mutation causing) effects. These effects are
most noted in frogs that live in the water with constant exposure – but what
about us exposed to plastics and other contaminants – there is more research to
be done.

Last summer I spoke to a frog researcher in Tuolumne meadows
from UC Berkeley.She had studies
several species living in high mountain lakes that are frozen solid for several
months each year.Those high mountain frogs,
she said, appeared healthy.Possibly due
to their isolation and to their long breeding cycle that could require more
than one year.